A fluid, as for example diesel fuel, in a pump circuit which comes in contact with a gas such as air often dissolves and/or entrains the air which is then transported throughout the fluid flow circuit. The entrained, compressible air in the fluid causes the normally incompressible fluid to be somewhat compressible which, in turn, may result in a miriad of problems. The problems vary from erratic volumetric efficiency of pumps to erratic readings from flow meters as both compressible and incompressible fluids flow through the circuit. Also, air pockets may form in the circuit as entrained air leaves the fluid which can result in foaming of the fluid and occasional slug flow patterns which possibly could damage equipment such as pumps.
It has been known in the prior art to provide a deaeration means in the pump circuit to remove air entrained in the fluid. It has also been known to overpressurize the fluid in order to increase the ability of a fluid to dissolve a greater amount of gas thereby reducing the amount of free gas bubbles.
One such deaeration means known to be used is an atmospheric reservoir having a top inlet and a bottom outlet, sized so as to hold the fluid long enough for the entrained air to slowly rise and pass out of the fluid. This approach somewhat alleviates the problems attending entrainment, however, the required reservoir may be prohibitively large. Additionally, the flow of fluid within the reservoir may develop flow patterns such that sufficient time is not provided to release the air. Providing a reservoir with baffles which avoid the flow patterns mentioned above is also known but the atmospheric release of entrained air requires substantially long hold up times and the reservoir itself often becomes a source of more entrainment as the fluid absorbs the air.
Another method known to deaerate fluid is to allow the incoming fluid to cascade into the reservoir over a baffle as a thin film as shown in U.S. Pat. No. 3,638,760 issued Feb. 1, 1972 to Heinz Lamm. The thin film cascading of the fluid enables the entrained air to be released from the fluid. This method may result in re-entrainment of air as the incoming fluid falls against the main body of fluid trapping air therebetween.
The present invention is directed to overcoming one or more of the problems as set forth above.